I have a question of an heating/cooling nature.

My office is upstairs over the garage. It abuts (a common wall) the attic storage area (about 800 sq ft) which has passive ventilation (roof ridge and eve vents) As you can imagine, it gets hot in there and also in my office.

My practice is to run the A/C while I am in the office working (HA!) and turn it off when I leave. I do this multiple times a day thinking I am saving energy.

Today I began to wonder if I was saving energy or using more energy having to cool a hot office when I come up. It was 82 degrees in the office this afternoon when I went up to peruse the various internet issues.

Was does the SIGForum brain works say? Leave the A/C on or turn it off as has been my habit?

Thanks,

RMD

The correct answer is do what ever you want. If you don't mind turning it back on and waiting for it to cool down then do that. If you would prefer it cool when you come in, leave it on. Turning it off likely saves a bit of energy overall depending on how often you use the space, but at the expense of comfort.

I think the typical thinking is to leave the AC on, but at a higher setting.

But I'd add, can you install, or add insulation to that wall to help the situation?

quote:

Originally posted by 6guns:
I think the typical thinking is to leave the AC on, but at a higher setting.

This is what I've heard as well, let it keep running but just less frequently to keep humidity in check and it won't have to work as hard starting over from say 76 degrees as 82.

If it is a plug in type I would buy one of those Kill A Watt things and see how much you are using both ways.
P3 P4400 Kill A Watt Electricity Usage Monitor https://a.co/d/0h45ef4I

More than cooling, is the de-humidification factor. You are first working to get the relative humidity below about 55%. If the unit has a dehumidify setting, leave it on that when you are not in the space.

My preference would be to simply set it where it cools to about 75 and bump it down to you comfort level when you are occupying that area.

I'm answering from my heat transfer and fluid flow courses in the Navy's nuclear power program.

The amount of heat transfer is proportional to the temperature difference. Between two spaces of different temperature, more heat gets transferred when you maintain the second room at the colder temperature. But when you turn off the A/C when you leave, the temperature rises in your room, the temperature differential decreases, and the amount of heat transfer decreases. You use less energy cooling down your room compared to keeping it constantly cooler even when you're not using the space.

quote:

Originally posted by Rey HRH:
I'm answering from my heat transfer and fluid flow courses in the Navy's nuclear power program.

The amount of heat transfer is proportional to the temperature difference. Between two spaces of different temperature, more heat gets transferred when you maintain the second room at the colder temperature. But when you turn off the A/C when you leave, the temperature rises in your room, the temperature differential decreases, and the amount of heat transfer decreases. You use less energy cooling down your room compared to keeping it constantly cooler even when you're not using the space.

There’s the answer. I need to pack that away in some unused brain cells so I can reference that in the future.

Getcha one of them newfangled thermostats that measure run time by day/week/month. Run a week in both modes and see. Try to do at a time when you use space similarly.

If'n you're one of those who's a'feared of the scary gubminnt tracking your power usage, swap back out when done and give it to your least favorite friend. Or karma here.

quote:

Originally posted by Rey HRH:
I'm answering from my heat transfer and fluid flow courses in the Navy's nuclear power program.

This is the answer I was looking for. Thanks to all.
RMD

quote:

Originally posted by rduckwor:

quote:

Originally posted by Rey HRH:
I'm answering from my heat transfer and fluid flow courses in the Navy's nuclear power program.

This is the answer I was looking for. Thanks to all.
RMD

If you have your own nuclear reactor, I doubt you have to worry about power costs!